As yet more heart breaking stories and images continue to pour out of the worst hit areas of the Philippines, desperately needed food and medical aid struggle to get in.

A family in Tacloban scoop up dirty water from a well using a long wooden stick attached to a small plastic container. They then strain it through a bright yellow t-shirt as a way of filtering it. The harmful bacteria will simply slip through the fibres. The family probably know this. But what choice do they have.

The main concern with dirty drinking water is the high risk of diarrhoeal disease. Children are most vulnerable. They can lose fluid quickly, become dehydrated and die as a result. The World Health Organisation has sent enough diarrhoea kits to treat 3000 people. They'll need many many more.

Four completely self-sufficient field hospitals from countries including Israel and Norway have landed in the Philippines, but are still waiting for flights and boats to get them to the worst hit areas.

WHO says everyone is working around the clock to get help to those who need it. But they admit it's an enormous challenge, which will continue for many weeks.

The peak danger period for this is between 10 days and one month after the event, according to the World Health Organization.

Unsafe food and a lack of access to safe water, lack of facilities for personal hygiene and safe sanitation arrangements all create a breading ground for infections, such as cholera.

With another tropical storm expected to hit the Philippines later this week, the need for shelter, safe water and sanitation is critical.

Basic needs

WHO is working with other humanitarian organisations to secure urgently needed water purification tablets.

Special diarrhoeal disease kits with medicines and supplies to treat 3,000 cases of acute diarrhoea are also en route - contaminated water is a frequent cause of diarrhoea.

Medicines and supplies to cover the basic health needs of 120,000 people for a month have been deployed.

And work has begun to strengthen an early warning system that can rapidly detect disease outbreaks and other public health threats.

WHO says the next steps will be critical.

It is how the survivors, rather than the dead, are managed that determines if and when an epidemic may occur. There has never been a documented case of an epidemic occurring after a natural disaster that could be traced to exposure to dead bodies.

Providing the most basic of needs - safe food, clean water, medicine and shelter - is what will make the difference now.

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